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Colloids and Interfaces
Special Issues
Locomotion of Colloidal Particles
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Locomotion of Colloidal Particles

A special issue of Colloids and Interfaces (ISSN 2504-5377).

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 18080

Special Issue Editor

Prof. Huan J. Keh

E-Mail Website
Guest Editor
Department of Chemical Engineering, National Taiwan University, Taipei 10617, Taiwan
Interests: colloid and interface science; electrokinetics; microhydrodynamics; aerosol science; transport phenomena

Special Issue Information

Dear Colleagues,

The area of Locomotion of Colloidal Particles has continued to receive much attention from researchers in the fields of chemical, mechanical, biomedical, and environmental engineering and science. The majority of this locomotion is fundamental in nature, but permits one to develop a rational understanding of many practical systems and industrial processes, such as centrifugation, agglomeration, flotation, spray drying, motion of cells in blood vessels, microfluidics, and aerosol technology. Conventional driving forces for the motion of hard, soft (polymer-adsorbed), and fluid particles include concentration gradients of the particles themselves (diffusion or Brownian motion), bulk velocities of the disperse media (convection), and gravitational or centrifugal fields (sedimentation). Another category of driving forces for the motion of colloidal particles involves a non-uniform imposed field (such as temperature, solute concentration, or electric potential) that interacts with the interfacial region at the surface of each particle. These phenomena include electrophoresis of charged particles in electrolyte solutions, diffusiophoresis of charged or uncharged particles, thermocapillary motion of liquid droplets or gas bubbles, thermophoresis and photophoresis of aerosol particles, and osmophoresis of semi-permeable vesicles. These phenomena find application in particle characterization, sensing, manipulation, assembly, separation, and transport in various physicochemical and biomedical systems. For this Special Issue, we seek fundamental and applied research contributions concerning the mobilities, mechanisms, dynamic behaviors, particle interactions (concentration effects), boundary effects, and other characteristics in the locomotion of colloidal particles.

Prof. Huan J. Keh
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Colloids and Interfaces is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Hard and soft particles
  • Liquid drops and gas bubbles
  • Charged particles in ionic solutions
  • Sedimentation
  • Electrophoresis
  • Diffusiophoresis
  • Thermophoresis
  • Thermocapillary motion

Published Papers (7 papers)

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Research

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14 pages, 3155 KiB  
Article
Electrophoretic Mobility and Electric Conductivity of Salt-Free Suspensions of Charged Soft Particles
by Wei C. Lin and Huan J. Keh
Colloids Interfaces 2021, 5(4), 45; https://doi.org/10.3390/colloids5040045 - 17 Oct 2021
Cited by 1 | Viewed by 2072
Abstract
A unit cell model is employed to analyze the electrophoresis and electric conduction in a concentrated suspension of spherical charged soft particles (each is a hard core coated with a porous polyelectrolyte layer) in a salt-free medium. The linearized Poisson–Boltzmann equation applicable to [...] Read more.
A unit cell model is employed to analyze the electrophoresis and electric conduction in a concentrated suspension of spherical charged soft particles (each is a hard core coated with a porous polyelectrolyte layer) in a salt-free medium. The linearized Poisson–Boltzmann equation applicable to a unit cell is solved for the equilibrium electrostatic potential distribution in the liquid solution containing the counterions only surrounding a soft particle. The counterionic continuity equation and modified Stokes/Brinkman equations are solved for the ionic electrochemical potential energy and fluid velocity distributions, respectively. Closed-form formulas for the electrophoretic mobility of the soft particles and effective electric conductivity of the suspension are derived, and the effect of particle interactions on these transport characteristics is interesting and significant. Same as the case in a suspension containing added electrolytes under the Debye–Hückel approximation, the scaled electrophoretic mobility in a salt-free suspension is an increasing function of the fixed charge density of the soft particles and decreases with increases in the core-to-particle radius ratio, ratio of the particle radius to the permeation length in the porous layer, and particle volume fraction, keeping the other parameters unchanged. The normalized effective electric conductivity of the salt-free suspension also increases with an increase in the fixed charge density and with a decrease in the core-to-particle radius ratio, but is not a monotonic function of the particle volume fraction. Full article
(This article belongs to the Special Issue Locomotion of Colloidal Particles)
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18 pages, 14483 KiB  
Article
Ordering and Dynamics of Interacting Colloidal Particles under Soft Confinement
by Salvador Herrera-Velarde, Edith C. Euán-Díaz and Ramón Castañeda-Priego
Colloids Interfaces 2021, 5(2), 29; https://doi.org/10.3390/colloids5020029 - 17 May 2021
Cited by 1 | Viewed by 2405
Abstract
Confinement can induce substantial changes in the physical properties of macromolecules in suspension. Soft confinement is a particular class of restriction where the boundaries that constraint the particles in a region of the space are not well-defined. This scenario leads to a broader [...] Read more.
Confinement can induce substantial changes in the physical properties of macromolecules in suspension. Soft confinement is a particular class of restriction where the boundaries that constraint the particles in a region of the space are not well-defined. This scenario leads to a broader structural and dynamical behavior than observed in systems enclosed between rigid walls. In this contribution, we study the ordering and diffusive properties of a two-dimensional colloidal model system subjected to a one-dimensional parabolic trap. Increasing the trap strength makes it possible to go through weak to strong confinement, allowing a dimensional transition from two- to one-dimension. The non-monotonic response of the static and dynamical properties to the gradual dimensionality change affects the system phase behavior. We find that the particle dynamics are connected to the structural transitions induced by the parabolic trap. In particular, at low and intermediate confinement regimes, complex structural and dynamical scenarios arise, where the softness of the external potential induces melting and freezing, resulting in faster and slower particle diffusion, respectively. Besides, at strong confinements, colloids move basically along one direction, and the whole system behaves structurally and dynamically similar to a one-dimensional colloidal system. Full article
(This article belongs to the Special Issue Locomotion of Colloidal Particles)
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16 pages, 1035 KiB  
Article
Axisymmetric Slow Motion of a Porous Spherical Particle in a Viscous Fluid Using Time Fractional Navier–Stokes Equation
by Jai Prakash and Chirala Satyanarayana
Colloids Interfaces 2021, 5(2), 24; https://doi.org/10.3390/colloids5020024 - 13 Apr 2021
Cited by 1 | Viewed by 2656
Abstract
In this paper, we present the unsteady translational motion of a porous spherical particle in an incompressible viscous fluid. In this case, the modified Navier–Stokes equation with fractional order time derivative is used for conservation of momentum external to the particle whereas modified [...] Read more.
In this paper, we present the unsteady translational motion of a porous spherical particle in an incompressible viscous fluid. In this case, the modified Navier–Stokes equation with fractional order time derivative is used for conservation of momentum external to the particle whereas modified Brinkman equation with fractional order time derivative is used internal to the particle to govern the fluid flow. Stress jump condition for the tangential stress along with continuity of normal stress and continuity of velocity vectors is used at the porous–liquid interface. The integral Laplace transform technique is employed to solve the governing equations in fluid and porous regions. Numerical inversion code in MATLAB is used to obtain the solution of the problem in the physical domain. Drag force experienced by the particle is obtained. The numerical results have been discussed with the aid of graphs for some specific flows, namely damping oscillation, sine oscillation and sudden motion. Our result shows a significant contribution of the jump coefficient and the fractional order parameter to the drag force. Full article
(This article belongs to the Special Issue Locomotion of Colloidal Particles)
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14 pages, 23062 KiB  
Article
Driven Transport of Dilute Polymer Solutions through Porous Media Comprising Interconnected Cavities
by Karthik Nagarajan and Shing Bor Chen
Colloids Interfaces 2021, 5(2), 22; https://doi.org/10.3390/colloids5020022 - 8 Apr 2021
Cited by 2 | Viewed by 2025
Abstract
Driven transport of dilute polymer solutions through porous media has been simulated using a recently proposed novel dissipative particle dynamics method satisfying the no-penetration and no-slip boundary conditions. The porous media is an array of overlapping spherical cavities arranged in a simple cubic [...] Read more.
Driven transport of dilute polymer solutions through porous media has been simulated using a recently proposed novel dissipative particle dynamics method satisfying the no-penetration and no-slip boundary conditions. The porous media is an array of overlapping spherical cavities arranged in a simple cubic lattice. Simulations were performed for linear, ring, and star polymers with 12 arms for two cases with the external force acting on (I) both polymer and solvent beads to model a pressure-driven flow; (II) polymer beads only, similar to electrophoresis. When the external force is in the direction of a principal axis, the extent of change in the polymers’ conformation and their alignment with the driving force is more significant for case I. These effects are most pronounced for linear chains, followed by rings and stars at the same molecular weight. Moreover, the polymer mean velocity is affected by its molecular weight and architecture as well as the direction and strength of the imposed force. Full article
(This article belongs to the Special Issue Locomotion of Colloidal Particles)
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Graphical abstract

14 pages, 2398 KiB  
Article
Electroosmosis and Electric Conduction of Electrolyte Solutions in Charge-Regulating Fibrous Media
by Wei L. Chen and Huan J. Keh
Colloids Interfaces 2021, 5(1), 19; https://doi.org/10.3390/colloids5010019 - 19 Mar 2021
Cited by 1 | Viewed by 2146
Abstract
An analytical study of the electroosmosis and electric conduction of electrolyte solutions in a fibrous medium composed of parallel charge-regulating cylinders with arbitrary electric double layer thickness is presented. A linearized charge regulation model was adopted for the association and dissociation reactions occurring [...] Read more.
An analytical study of the electroosmosis and electric conduction of electrolyte solutions in a fibrous medium composed of parallel charge-regulating cylinders with arbitrary electric double layer thickness is presented. A linearized charge regulation model was adopted for the association and dissociation reactions occurring at the amphoteric functional groups over the surfaces of the cylinders, and a unit cell model was employed to accommodate interactions among the cylinders. The electrokinetic equations governing the ionic concentration, electric potential, and liquid flow fields were solved at low zeta potential for the cylinders. Explicit formulas for the electroosmotic mobility and effective electric conductivity in the fiber matrix were obtained. The results indicate that the charge regulation characteristics, such as the equilibrium constants of the reactions occurring at the cylinders’ surfaces and the bulk concentration of the charge-determining ions, influence the surface charge density and potential, electroosmotic mobility, and effective electric conductivity substantially. Full article
(This article belongs to the Special Issue Locomotion of Colloidal Particles)
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13 pages, 1862 KiB  
Article
Numerical Simulation of the Distribution of In Situ Cigarette Combustion-Generated Particulate Matter
by Shi Chen, Hanqing Liu, Zhiguo Sun and Hongyong Xie
Colloids Interfaces 2020, 4(4), 59; https://doi.org/10.3390/colloids4040059 - 15 Dec 2020
Cited by 1 | Viewed by 2379
Abstract
This paper has established a two-dimensional (2D) mathematical model for the generation, growth, and deposition of cigarette total particulate matter (TPM) in the smoldering state. The model has covered the chemical reactions and mass transfer as well as the mechanism of generation, flow, [...] Read more.
This paper has established a two-dimensional (2D) mathematical model for the generation, growth, and deposition of cigarette total particulate matter (TPM) in the smoldering state. The model has covered the chemical reactions and mass transfer as well as the mechanism of generation, flow, and condensation of particulate matter inside a burning cigarette. Cigarette smoke was generated by puffing under a constant pressure, and the pressure of the filter outlet was −274 Pa. The peak of the concentration of particulate matter was spatially overlapped with the peaks of pyrolysis and oxidation. Pertaining to the cross section of the cigarette at the same axial position, the peak of the diameter of particulate matter along the radial distribution first appeared in the zone near the edge of the cigarette cross section, and then gradually moved to the center of the cigarette with the cigarette smoke moving away from the combustion cone. The maximum number density of particulate matter calculated by the 2D mathematical model at the same axial position of the cigarette and the corresponding particle diameter, as well as the filtration efficiency of the filter rod, are in good accordance with the experimental data reported in previous studies. Full article
(This article belongs to the Special Issue Locomotion of Colloidal Particles)
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Review

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16 pages, 16412 KiB  
Review
Effect of Produced Sand Particles and Fines on Scale Inhibitor: A Review
by Uche C. Anyanwu and Gbenga F. Oluyemi
Colloids Interfaces 2021, 5(3), 35; https://doi.org/10.3390/colloids5030035 - 23 Jun 2021
Cited by 2 | Viewed by 3525
Abstract
Application of scale inhibitors in oil and gas production is aimed at mitigating scale blockage during production. Many experimental, mathematical, and numerical simulation modeling works have been carried out to evaluate behavior, performance, and interaction of the scale inhibitor chemicals within porous media [...] Read more.
Application of scale inhibitors in oil and gas production is aimed at mitigating scale blockage during production. Many experimental, mathematical, and numerical simulation modeling works have been carried out to evaluate behavior, performance, and interaction of the scale inhibitor chemicals within porous media in relation to their efficiency in solving scale problem. However, the mechanisms underpinning scale inhibitors performance are not well published. Some research works have shown theoretically that not all scale inhibitors pumped into the formation adsorb onto the formation rock. Some of the inhibitors may adsorb on produced loose sand grains or colloidal fine sand particles which float and flow within the pore spaces along with the scale inhibitor mostly in unconsolidated reservoirs This paper provides a review of research work on the effect of produced loose sand or colloidal fine particles flow on polyphosphonates and polyphosphinopolymer scale inhibitors performances during crude production. Full article
(This article belongs to the Special Issue Locomotion of Colloidal Particles)
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